SumTree.java

package com.interview.tree;


class Count{
    int size;
}

/**
 * http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-sumtree/
 * A SumTree is a Binary Tree where the value of a node is equal to sum of the nodes present 
 * in its left subtree and right subtree
 */
public class SumTree {

    public boolean isSumTree(Node root){
        Count count = new Count();
        return isSumTree(root,count);
    }
    
    private boolean isSumTree(Node root,Count count){
        if(root == null){
            return true;
        }
        if(root.left == null && root.right == null){
            count.size = root.data;
            return true;
        }
        Count leftCount = new Count();
        Count rightCount = new Count();
        boolean isLeft = isSumTree(root.left,leftCount);
        boolean isRight = isSumTree(root.right,rightCount);
        count.size = root.data + leftCount.size + rightCount.size;
        return isLeft && isRight && root.data == (leftCount.size + rightCount.size);
    }
    
    public static void main(String args[]){
        ConstructTreeFromInOrderPreOrder ctf = new ConstructTreeFromInOrderPreOrder();
        int inorder[] = {4,10,6,46,11,13,2};
        int preorder[] = {46,10,4,6,13,11,2};
        Node root = ctf.createTree(inorder, preorder);
        SumTree st = new SumTree();
        System.out.println(st.isSumTree(root));
    }
}